Energy conservation assumes an ever more important place in today's technology. Increased fuel costs make it desirable to use energy efficiently. A heat pump system, especially one which capitalizes on the use of what would otherwise be waste heat, would be a desirable conservation unit.
Commercially available heat pump systems usually use heat from the ambient air or from the discharge of an air conditioner to heat water for household use. These systems are impractical or infeasible in colder climates. Because conservation is particularly important in the colder climates, an alternative system is desirable.
In U.S. Pat. No. 2,575,325, a heat pump system is capable of supplying heated water for home use with increased efficiency. The system utilizes the heat of waste liquids generated when the heated water has been used and is being discharged. Alternatively, heat from an air conditioner may be used. Heat exchange between the refrigerant and wastewater occurs in a liquid discharge receiver vessel. If the wastewater flows directly through the receiver vessel, an excessively costly heat exchanger is required. If the wastewater flow is slowed or stopped, particulates in the water will settle, in some circumstances causing the vessel and lines to become clogged.
In U.S. Pat. No. 2,484,371, a pump utilizing the heat of liquids, especially waste products, provides space heating for the interior of a building. The pump uses sewage as its primary heat source. Use of this untreated waste product will lead to heat exchanger and drain line fouling and clogging. The heat exchanger coil is directly immersed in the liquid waste so that efficient heat transfer is possible at all times (col. 3, lines 66-71).
In U.S. Pat. No. 2,751,761, a combination heat pump and water heater uses the ground as a source of heat from which to heat water for home use.
In their book, Chemical Engineering Thermodynamics, The Study of Energy, Entropy, and Equilibrium (.sctn. 7.11), Balzhiser, Samuels, and Eliassen discuss the basic thermodynamic principles of a heat pump. In particular, at pages 282-283, the thermodynamic efficiency of a home heat pump air conditioner using Freon-22 as a working fluid to provide 36,000 Btu/hr of cooling capacity is calculated, showing about a 45,000 Btu/hr condenser load (heating capacity).